How to set privilaged mode in ARM Cortex-A8?

Question

I have to use Neon co-processor of Ti Sitara am335x processor. To enable neon, I have to enable the 30th bit of FPEXC(floating point exceptional register). For that I need to get into the privilaged/system mode.

Some of them suggested to attain this by sending interrupts. How to do that for cortex A8? Could anyone explain me?

Thanks.

Are you running baremetal or is there an operating system? – tangrs Jun 19 '15 at 04:57 — tangrs, Jun 19 '15 at 04:57

Arun Valiaparambil · Answer 1 · 2015-06-19T08:49:52.603

0

You can use interrupts or svc to get into privileged mode, but then your OS code will be running and you would have no control. How do you then propose to enable neon by accessing fpexc?

Your best bet will be recompile your OS with floating point / neon enabled. This will enable the vfp/neon unit at bootup. Also when vfp/neon is enabled ,the task switcher will need to save restore the fpu registers along with general purpose registers.

edited Jun 19 '15 at 08:49

answered Jun 18 '15 at 19:05

Arun Valiaparambil

545
3
7

I am using TI sdk-7.0. Where should I give this option? In Makefile? – Rak Jun 19 '15 at 06:36
change the Kernel Config to add support for Neon and rebuild. You should be good to go. – Arun Valiaparambil Jun 25 '15 at 18:01

How to set privilaged mode in ARM Cortex-A8?

1 Answers1